268656 Nonspherical Janus Particles At an Oil-Water Interface

Tuesday, October 30, 2012: 8:35 AM
413 (Convention Center )
Bum Jun Park1, Chang-Hyung Choi2, Chang-Soo Lee2 and Daeyeon Lee1, (1)Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, PA, (2)Department of Chemical Engineering, Chungnam National University, Daejeon, South Korea

We study the configurations of nonspherical Janus particles such as ellipsoids, dumbbells, and cylinders at an oil-water interface. To determine the equilibrium configurations, we numerically calculate and minimize the attachment energy of each Janus particle as a function of the orientation angle as well as the vertical displacement with respect to the interface. We find that the equilibrium orientation of nonspherical Janus particles strongly depends on the particle characteristics, such as their size, shape, aspect ratio, surface wettability, and the location of the Janus boundary. In general, Janus particles with a high aspect ratio or a small difference in wettability between the two sides tend to have tilted orientations. Under certain circumstances, Janus ellipsoids and cylinder have meta-stable configuration as indicated by the presence of secondary minima in the attachment energy profile.  The size of Janus particles plays an important role in determining the distribution of orientation angles of these particles at the fluid-fluid interface. Janus dumbbells, on the other hand, possess primary energy minimum only, indicating that their orientation at the fluid interface would be homogenous.  Our study provides a detailed guidance for designing and synthesizing the non-spherical Janus particles, especially for their applications in multiphase fluid mixture stabilization.

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